[Qt-interest] QTimer on Windows in Unreliable for Small (16ms - 30ms) Delays

[Josiah Bryan]

I realize I may be out of line here and this may not be 
"feasible"....but, I'll ask anyway!

I'm trying to do video playback with Qt. (The end goal is some video 
with text over top - song lyrics for church and the like.) I'm using 
ffmpeg (libavcodec, etc) as the decoder. No problems there - works 
great. The problem comes in getting the frame onto the screen in a 
timely fashion.

I've got the code to compute the optimal delay between frames, based on 
elapsed time, etc. It normally works out to around 33ms for a 30 fps 
video. I set a timer that throws a signal once the time is up for that 
frame. The other end of that signal just draws the frame.

The problem, specifically, is that  about once every 20 - 60 frames, the 
timer wacks out and doesn't fire for around 1000 ms - no where *near* 
the requested 30ms or whatever.

I'm just doing:
QTimer::singleShot(actual_delay, this, SLOT(displayFrame()));

I've tried *everything* I can think of to figure out why its randomly 
taking way longer than requested - raised the priority of the executable 
thru task manager, using a QTimer object instead of 
QTimer::singleShot(), any other misc ideas I can think of. I've been 
googling for *everything* - no answers, nothing seems to help. I've even 
seen metion of something like qt_win_simple_timers or something like 
that - compile errors, didn't help. I tried using windows timer queues - 
I forget the function names - but compile errors there.

Anyway, anyone have any ideas? Or, even alternatives to playing videos 
in QT? (Phonon isn't working for me.)

Thanks,
-josiah